I apologize for the delayed response and I hope your question has been answered in the interim. Based on your description, the process you need to complete is an Assumption of Liability (AOL). If you currently have unlimited data the AOL will not cause the feature to fall off, you will be grandfathered.
Here are the steps to begin the AOL process:
Additionally I sent you an email detailing the requirements that need to be met in order the complete the AOL process. I am confident this information is helpful. Please let me know if you have any additional questions.
Thank you for your contribution to our community forums,